The long-term objective of this research is to provide information on the mode of iron absorption in microbial species, with emphasis on the molecular mechanism of regulation. Insufficient iron leads to anemia in animal subject and to impaired crop yields in plants. Excess iron promotes infection and results in generation of tissue damaging oxygen radicals. A combination of biochemical and molecular biological methods will be used for the study of iron absorption in two enteric bacterial species, Escherichia coli and Salmonella typhimurium, and in the single-celled basidiomycetous fungus, Rhodotorula pilimanae.